What is time weighted average OSHA?

Time-weighted average (TWA) is a method of calculating a worker’s daily exposure to hazardous substances such as dust, fumes, chemicals, gases, or vapors. It is averaged to an 8-hour workday or 40-hour week, along with the average levels of exposure to the hazardous substance and the time spent in that area.

What is meant by time weighted average?

A time-weighted average is equal to the sum of the portion of each time period (as a decimal, such as 0.25 hour) multiplied by the levels of the substance or agent during the time period divided by the hours in the workday (usually 8 hours).

What is the OSHA PEL 8 hour time weighted average for toluene?

In the final rule, OSHA is establishing an 8-hour TWA PEL of 100 ppm and a STEL of 150 ppm for toluene.

What is the difference between STEL and TWA?

A Time Weighted Average (TWA) is a TLV(R) based on a 8-hour workday and a 40-hour workweek. For example the TWA for carbon monoxide is 25 ppm. This means that an average of 25 ppm is considered to be the safe TLV(R) for an 8-hour workday. A Short Term Exposure Limit (STEL) is a TLV(R) based on a 15 minute average.

What is the difference between OEL and TWA?

Explanation: OEL is the most restrictive value selected between various threshold limits. It’s comparable to TLV and PEL. TWA is a way of specifying any of those threshold limits values: the 8 hr average.

What is a time weighted average exposure limit?

Time weighted average (TWA) is the average exposure to any hazardous gas in the workplace based on an eight-hour workday or 40-hour work week. It is the maximum amount one may be exposed to without experiencing significant adverse health effects over said period.

How is OSHA PEL calculated?

An example with values inserted would be if an employee was exposed to Substance A which has an eight-hour TWA of 100 ppm. The exposure is as follows: Two hours exposure at 150 ppm, two hours at 75 ppm and two hours at 50ppm (2×150 + 2×75 + 4×50)÷8 = 81.25 ppm .

What is TLV TWA and STEL?